Aerodynamic-type flameholder



July 4, 1967 G. E. CANUEL AERODYNAMIC-TYPE FLAMEHOLDER Original Filed June 19, 1961 FIGJ INVEN'TQR GEORGE E CANUEI- BYYM Z ATTORNEY United States Patent 3,328,958 AERODYNAMIC-TYPE FLAMEHOLDER George E. Canuel, Manchester, Conn., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Continuation of application Ser. No. 118,101, June 19, 1961. This application June 5, 1963, Ser. No. 286,135 3 Claims. (Cl. 6039.72)

This is a continuation application of United States patent application Ser. No. 118,101 now abandoned on improvements in Aerodynamic-Type Flameholder for ll)9u6ct-Burning Fan, by George E. Canuel, filed June 19,

It is an object of this invention to teach a duct burning turbo-fan engine wherein a fuel-air mixture is provided to the bypass duct for combustion therein by apparatus which presents minimum resistance to flow therethrough and which forms an aerodynamic flameholder.

It is a further object of this invention to teach a duct burning turbo-fan engine wherein concentric ducts define concentric hot gas and cold air passages and wherein a rich fuel-air mixture is provided to the central portion of the cold air passage through a hollow airfoil shaped ring centrally located therein and shaped and positioned to present minimum resistance to flow and having circumferentially extending slot shaped apertures or holes in the walls thereof extending normal to the direction of air therethru so that as the rich fuel-air mixture is passed thru said slots or holes and into said cold air passage, a combustion supporting stagnation zone is formed therein by an aerodynamic flameholder formed bythe fuel-air mixture pattern so established.

It is a further object of this invention to teach such an engine wherein the air which is provided to make said fuel-air mixture comes from available air supply in the engine such as from the compressor, burner or turbine.

It is still a further object of this invention to teach injection of a fuel-air mixture into the cold fan air passage of a duct burning turbo-fan engine which is small in size so as to present no wake or loss during no burning operation and which creates a substantial stagnation zone by injecting a fuel-air mixture into the cold air stream normal to the direction of flow to establish a fuel-air mixture pattern which is an aerodynamic flameholder.

Other objects and advantages will be apparent from the specification and claims and from the accompanying drawings which illustrate an embodiment of the invention.

FIGURE 1 is an external showing of a ducted burning turbo-fan engine partially broken away to illustrate my invention.

FIGURE 2 is a cross-sectional showing of my fuel-air mixture distributing an aerodynamic flameholder creating airfoil ring.

Referring to FIG. 1 we see duct burning turbo-fan engine 10 which is of generally circular cross-section and concentric about axis 12 and which includes an engine case 14 and a fan duct 16 each of which are of circular cross-section and concentric about axis 12. Engine case 14 envelops compressor 18, burner 20 and turbine 22 and culminates in exhaust duct 24 which defines circular exhaust outlet 26 through which the hot engine exhaust gases are discharged to atmosphere. These engine exhaust gases are formed in typical fashion by air which enters engine inlet 28, is compressed in passing through compressor section 18, has heat added thereto in passing through burner 20 and has sufficient energy extracted therefrom in passing through turbine 22 to drive compressor 18 and is then discharged to atmosphere through exhaust duct 24 which forms part of engine case 14.

Fan duct 16 envelopes all of engine case 14 and either the forward portion of compressor 18 or a separate com- Patented July 4, 1967 pressor section 30 and cooperates with engine case 14 to define annular cold fan air passage 32 which extends from the forward end of engine case 14 and terminates in annular exhaust outlet 34 which is coplanar with engine case outlet 26. It will therefore be seen that some of the air which enters inlet section 28 and is compressed by compressor section 30 then passes through annular cold fan air passage 32 and is burned therein in a fashion to be described hereinafter to have added energy imparted thereto and is eventually discharged to atmosphere through exhaust outlet 34.

. It is believed that the above description of engine 10 will be sufiicient for present purposes, but for a more particular description, reference may be had to US. Patent No. 2,887,845.

The aforementioned additional energy is added to the cold air passing through annular passage 32 primarily by means of injecting therein a rich fuel-air mixture of a ratio of about 1.0 through airfoil shaped annular ring 40 which forms an aerodynamic flameholder and which fuel-air mixture is ignited by any convenient means such as spark plug 42. Fuel is supplied to airfoil ring 40 through line 44 from pump 46 which draws fuel from reservoir 48. Air is mixed with fuel in line 44 prior to reaching ring 40 and this air is supplied, for example, through line 50 from compressor section 18. It should be borne in mind that this air could as well have been supplied from burner section 20 or turbine section 22. If deemed desirable, a secondary fuel injection system such as perforated spray bars 52, which are radially extending and circumferentially positioned about fan duct 16 may be utilized. Fuel is supplied to spray bars 52 from pump 54 by way of line 53 with flow regulating valve 55 therein and manifold ring 56. This secondary fuel system will be used during takeoff or climb for maximum thrust augmentation whereas for low augmentation, flameholder 40 would be used with fuel and air control thereto by valves 57 and 59, respectively.

Referring to FIG. 2 we see the airfoil shaped fuel-air mixture distributing ring 40 in greater particularity. It will be noted that both ring 40 and line 44, which are in communication therewith, are of hollow construction to permit the passage of a rich fuel-air mixture therethrough. Ring 40 is of airfoil shape so as to present minimum resistance to air flow through cold gas passage 32 and is concentric about its cross-sectional axis 60, which extends parallel to engine axis 12. Ring 40 includes circumferentially extending and slot shaped apertures 62 and 64 in the outer surface 66 and inner surface 68, respectively, thereof. Slots 62 and 64 have a center line or axis 70 which extends normal or perpendicular to axes 60 and 12. Due to the perpendicular attitude of slots 62 and 64 with respect to axes 12 and 60 and hence the direction of flow through cold air passage 32, the rich fuelair mixture which is injected therethrough into the air passing through annular cold air passage 32 creates a flow pattern as shown in the dotted lines in FIG. 2 to establish an aerodynamic flameholder and hence a stagnation zone 72 downstream thereof in which the fuel air mixture may burn and impart heat and therefore energy to the cold air. Accordingly, due to the stagnation region forming or flameholder function performed by the fuelair mixture so injected, airfoil ring 40 may be made of very small size and thereby create no loss during periods of engine operation when burning is not occurring in cold air passage 32 and yet is capable of creating a fuelair mixture pattern which is an aerodynamic flameholder and provide the stagnation zone necessary to permit combustion in the cold air passage when the aforementioned fuel-air mixture is discharged therefrom as described above.

It has been found preferable that the fuel-air ratio discharged through slots 62 and 64 be about 1.0, that is, equal parts of fuel and air, and that the width or axial dimension of the slots be about 0.03 inch. For example, if the fuel used is conventional JP fuel, the optimum fuel air ratio is 1.35: 1.

It is to be understood that the invention is not limited to the specific embodiment herein illustrated and described but may be used in other ways without departure from its spirit as defined by the following claims.

I claim:

1. The method of supporting combustion in a cold air stream by producing an aerodynamic flameholder comprising providing a hollow-aerodynamic shaped flameholder within said stream, positioning said fiameholder to present minimum resistance to airflow, then discharging a rich fuel-air mixture of substantially equal parts of fuel and air through apertures in the wall of the flameholder in a direction substantially normally to the direction of cold air flow, then igniting the injected fuel-air mixture.

2. The method of supporting combustion in an annular cold air duct comprising providing a hollow flameholder ring of aerodynamic cross-section positioned concentrically Within the duct to present minimum resistance to air flow, then injecting a rich fuel air mixture of approximately equal parts of fuel and air through apertures in opposite walls of the fiameholder ring in a direction substantially perpendicular to the direction of air flow through the duct, then igniting the injected fuel -air mixture.

3. The method as in claim 2 wherein the fuel is JP fuel and the fuel-air ratio is about 1.35: 1.

References Cited UNITED STATES PATENTS 2,611,239 9/1952 Briggs 39.14 2,867,085 1/1959 Saboe 603S.6 2,887,845 5/1959 Hagen 60-3982 2,979,899 4/1961 Salmon et a1 60-3974 X FOREIGN PATENTS 165,939 11/1955 Australia. 712,843 8/ 1954 Great Britain.

JULIUS E. WEST, Primary Examiner.

SAMUEL FEINBERG, BENJAMIN A. BORCHELT, Examiners.

G. L. PETERSON, G. H. GLANZMAN,

Assistant Examiners. 

1. THE METHOD OF SUPPORTING COMBUSTION IN A COLD AIR STREAM BY PRODUCING AN AERODYNAMIC FLAMEHOLDER COMPRISING PROVIDING A HOLLOW-AERODYNAMIC SHAPED FLAMEHOLDER WITHIN SAID STREAM, POSITIONING SAID FLAMEHOLDER TO PRESENT MINIMUM RESISTANCE TO AIRFLOW, THEN DISCHARGING A RICH FUEL-AIR MIXTURE OF SUBSTANTIALLY EQUAL PARTS OF FUEL AND AIR THROUGH APERTURES IN THE WALL OF THE FLAMEHOLDER IN A DIRECTION SUBSTANTIALLY NORMALLY TO THE DIRECTION OF COLD AIR FLOW, THEN IGNITING THE INJECTED FUEL-AIR MIXTURE. 